1. Field of the Invention
The present invention relates to the all-optical logic AND operation in a SOA (semiconductor optical amplifier) -based Mach-Zehnder interferometer. More particularly, it relates to the technology making feasible ultra high-speed logic operations while maintaining a small size and a low input power by utilizing a cross-phase modulation (XPM) wavelength modulator composed of semiconductor optical amplifiers in the form of a Mach-Zehnder interferometer with nonlinear characteristics.
2. Description of the Related Art
Logic operations based on optics have been receiving a lot of attention as a solution to the limitations of speed and operation capacity of the electronic elements. The ultra high-speed all-optical logic operations take advantage of the nonlinearity of most materials. The logic operations of Sagnac interferometer type, which make use of the nonlinear Kerr effect of optical fibers, have been mainly studied. However, the problem with using the nonlinearity of the optical fibers lies in the fact that one requires a sufficiently large optical intensity and that the size of the circuit has to be large. With the recent announcement of devices such as TOAD (Terahertz optical asymmetric demultiplexer?), which utilizes the nonlinear gain saturation phenomena of the semiconductor optical amplifier, not only has the size been reduced but also the intensity of the optics used was also able to be reduced.
The optical logic operations using an interferometer can be performed not only through the Sagnac interferometer, but also the Mach-Zehnder interferometer, which is composed of waveguides with nonlinear characteristics, and the Michelson interferometer. Therefore, by using an optical device integrated with semiconductor optical amplifiers to carry out logic operations, the reduction in size and power consumption is made possible.
The idea behind the present invention is the solution of the above stated problem by utilizing a XPM wavelength converter constituted of semiconductor optical amplifiers in the form of a Mach-Zehnder interferometer. This will result in the production of all-optical AND logic operation method by using the SOA-based Mach-Zehnder interferometer, which makes possible an ultra high-speed logic calculator of small size and low input power.
To achieve the above-mentioned goals of the present invention, the invention is constituted of an optical fiber mode-lock laser capable of producing optical pulses for a certain operation speed; an optical attenuator to dampen the optical output; a multiplexer; the optical delay line; a 3-dB optical fiber coupler for splitting the optical intensity 50:50 ; a polarization controller to attain the polarization that will result in the optimized optical wavelength efficiency; the second optical delay line; an optical isolator transmitting the optical waves; XPM wavelength converter; Erbium doped optical fiber amplifier; optical wavelength filter; and an optical signal analyzer. Wherein the current in the waveguide portion of the XPM wavelength modulator is adequately controlled so that the input signal A is normally outputted as signal C at the output port by controlling the current of the two wave guides which constitute the interferometer. The delay time of signal A is controlled to be synchronized with signal B so that the All-Optical Logic AND operation in a SOA-Based Mach-Zehnder Interferometer is carried out.